/*
* /proc/sys support
*/
#include <linux/sysctl.h>
#include <linux/proc_fs.h>
#include <linux/security.h>
#include "internal.h"
static struct dentry_operations proc_sys_dentry_operations;
static const struct file_operations proc_sys_file_operations;
static const struct inode_operations proc_sys_inode_operations;
static void proc_sys_refresh_inode(struct inode *inode, struct ctl_table *table)
{
/* Refresh the cached information bits in the inode */
if (table) {
inode->i_uid = 0;
inode->i_gid = 0;
inode->i_mode = table->mode;
if (table->proc_handler) {
inode->i_mode |= S_IFREG;
inode->i_nlink = 1;
} else {
inode->i_mode |= S_IFDIR;
inode->i_nlink = 0; /* It is too hard to figure out */
}
}
}
static struct inode *proc_sys_make_inode(struct inode *dir, struct ctl_table *table)
{
struct inode *inode;
struct proc_inode *dir_ei, *ei;
int depth;
inode = new_inode(dir->i_sb);
if (!inode)
goto out;
/* A directory is always one deeper than it's parent */
dir_ei = PROC_I(dir);
depth = dir_ei->fd + 1;
ei = PROC_I(inode);
ei->fd = depth;
inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
inode->i_op = &proc_sys_inode_operations;
inode->i_fop = &proc_sys_file_operations;
inode->i_flags |= S_PRIVATE; /* tell selinux to ignore this inode */
proc_sys_refresh_inode(inode, table);
out:
return inode;
}
static struct dentry *proc_sys_ancestor(struct dentry *dentry, int depth)
{
for (;;) {
struct proc_inode *ei;
ei = PROC_I(dentry->d_inode);
if (ei->fd == depth)
break; /* found */
dentry = dentry->d_parent;
}
return dentry;
}
static struct ctl_table *proc_sys_lookup_table_one(struct ctl_table *table,
struct qstr *name)
{
int len;
for ( ; table->ctl_name || table->procname; table++) {
if (!table->procname)
continue;
len = strlen(table->procname);
if (len != name->len)
continue;
if (memcmp(table->procname, name->name, len) != 0)
continue;
/* I have a match */
return table;
}
return NULL;
}
static struct ctl_table *proc_sys_lookup_table(struct dentry *dentry,
struct ctl_table *table)
{
struct dentry *ancestor;
struct proc_inode *ei;
int depth, i;
ei = PROC_I(dentry->d_inode);
depth = ei->fd;
if (depth == 0)
return table;
for (i = 1; table && (i <= depth); i++) {
ancestor = proc_sys_ancestor(dentry, i);
table = proc_sys_lookup_table_one(table, &ancestor->d_name);
if (table)
table = table->child;
}
return table;
}
static struct ctl_table *proc_sys_lookup_entry(struct dentry *dparent,
struct qstr *name,
struct ctl_table *table)
{
table = proc_sys_lookup_table(dparent, table);
if (table)
table = proc_sys_lookup_table_one(table, name);
return table;
}
static struct ctl_table *do_proc_sys_lookup(struct dentry *parent,
struct qstr *name,
struct ctl_table_header **ptr)
{
struct ctl_table_header *head;
struct ctl_table *table = NULL;
for (head = sysctl_head_next(NULL); head;
head = sysctl_head_next(head)) {
table = proc_sys_lookup_entry(parent, name, head->ctl_table);
if (table)
break;
}
*ptr = head;
return table;
}
static struct dentry *proc_sys_lookup(struct inode *dir, struct dentry *dentry,
struct nameidata *nd)
{
struct ctl_table_header *head;
struct inode *inode;
struct dentry *err;
struct ctl_table *table;
err = ERR_PTR(-ENOENT);
table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head);
if (!table)
goto out;
err = ERR_PTR(-ENOMEM);
inode = proc_sys_make_inode(dir, table);
if (!inode)
goto out;
err = NULL;
dentry->d_op = &proc_sys_dentry_operations;
d_add(dentry, inode);
out:
sysctl_head_finish(head);
return err;
}
static ssize_t proc_sys_read(struct file *filp, char __user *buf,
size_t count, loff_t *ppos)
{
struct dentry *dentry = filp->f_dentry;
struct ctl_table_header *head;
struct ctl_table *table;
ssize_t error;
size_t res;
table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head);
/* Has the sysctl entry disappeared on us? */
error = -ENOENT;
if (!table)
goto out;
/* Has the sysctl entry been replaced by a directory? */
error = -EISDIR;
if (!table->proc_handler)
goto out;
/*
* At this point we know that the sysctl was not unregistered
* and won't be until we finish.
*/
error = -EPERM;
if (sysctl_perm(table, MAY_READ))
goto out;
/* careful: calling conventions are nasty here */
res = count;
error = table->proc_handler(table, 0, filp, buf, &res, ppos);
if (!error)
error = res;
out:
sysctl_head_finish(head);
return error;
}
static ssize_t proc_sys_write(struct file *filp, const char __user *buf,
size_t count, loff_t *ppos)
{
struct dentry *dentry = filp->f_dentry;
struct ctl_table_header *head;
struct ctl_table *table;
ssize_t error;
size_t res;
table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head);
/* Has the sysctl entry disappeared on us? */
error = -ENOENT;
if (!table)
goto out;
/* Has the sysctl entry been replaced by a directory? */
error = -EISDIR;
if (!table->proc_handler)
goto out;
/*
* At this point we know that the sysctl was not unregistered
* and won't be until we finish.
*/
error = -EPERM;
if (sysctl_perm(table, MAY_WRITE))
goto out;
/* careful: calling conventions are nasty here */
res = count;
error = table->proc_handler(table, 1, filp, (char __user *)buf,
&res, ppos);
if (!error)
error = res;
out:
sysctl_head_finish(head);
return error;
}
static int proc_sys_fill_cache(struct file *filp, void *dirent,
filldir_t filldir, struct ctl_table *table)
{
struct ctl_table_header *head;
struct ctl_table *child_table = NULL;
struct dentry *child, *dir = filp->f_path.dentry;
struct inode *inode;
struct qstr qname;
ino_t ino = 0;
unsigned type = DT_UNKNOWN;
int ret;
qname.name = table->procname;
qname.len = strlen(table->procname);
qname.hash = full_name_hash(qname.name, qname.len);
/* Suppress duplicates.
* Only fill a directory entry if it is the value that
* an ordinary lookup of that name returns. Hide all
* others.
*
* If we ever cache this translation in the dcache
* I should do a dcache lookup first. But for now
* it is just simpler not to.
*/
ret = 0;
child_table = do_proc_sys_lookup(dir, &qname, &head);
sysctl_head_finish(head);
if (child_table != table)
return 0;
child = d_lookup(dir, &qname);
if (!child) {
struct dentry *new;
new = d_alloc(dir, &qname);
if (new) {
inode = proc_sys_make_inode(dir->d_inode, table);
if (!inode)
child = ERR_PTR(-ENOMEM);
else {
new->d_op = &proc_sys_dentry_operations;
d_add(new, inode);
}
if (child)
dput(new);
else
child = new;
}
}
if (!child || IS_ERR(child) || !child->d_inode)
goto end_instantiate;
inode = child->d_inode;
if (inode) {
ino = inode->i_ino;
type = inode->i_mode >> 12;
}
dput(child);
end_instantiate:
if (!ino)
ino= find_inode_number(dir, &qname);
if (!ino)
ino = 1;
return filldir(dirent, qname.name, qname.len, filp->f_pos, ino, type);
}
static int proc_sys_readdir(struct file *filp, void *dirent, filldir_t filldir)
{
struct dentry *dentry = filp->f_dentry;
struct inode *inode = dentry->d_inode;
struct ctl_table_header *head = NULL;
struct ctl_table *table;
unsigned long pos;
int ret;
ret = -ENOTDIR;
if (!S_ISDIR(inode->i_mode))
goto out;
ret = 0;
/* Avoid a switch here: arm builds fail with missing __cmpdi2 */
if (filp->f_pos == 0) {
if (filldir(dirent, ".", 1, filp->f_pos,
inode->i_ino, DT_DIR) < 0)
goto out;
filp->f_pos++;
}
if (filp->f_pos == 1) {
if (filldir(dirent, "..", 2, filp->f_pos,
parent_ino(dentry), DT_DIR) < 0)
goto out;
filp->f_pos++;
}
pos = 2;
/* - Find each instance of the directory
* - Read all entries in each instance
* - Before returning an entry to user space lookup the entry
* by name and if I find a different entry don't return
* this one because it means it is a buried dup.
* For sysctl this should only happen for directory entries.
*/
for (head = sysctl_head_next(NULL); head; head = sysctl_head_next(head)) {
table = proc_sys_lookup_table(dentry, head->ctl_table);
if (!table)
continue;
for (; table->ctl_name || table->procname; table++, pos++) {
/* Can't do anything without a proc name */
if (!table->procname)
continue;
if (pos < filp->f_pos)
continue;
if (proc_sys_fill_cache(filp, dirent, filldir, table) < 0)
goto out;
filp->f_pos = pos + 1;
}
}
ret = 1;
out:
sysctl_head_finish(head);
return ret;
}
static int proc_sys_permission(struct inode *inode, int mask, struct nameidata *nd)
{
/*
* sysctl entries that are not writeable,
* are _NOT_ writeable, capabilities or not.
*/
struct ctl_table_header *head;
struct ctl_table *table;
struct dentry *dentry;
int mode;
int depth;
int error;
head = NULL;
depth = PROC_I(inode)->fd;
/* First check the cached permissions, in case we don't have
* enough information to lookup the sysctl table entry.
*/
error = -EACCES;
mode = inode->i_mode;
if (current->euid == 0)
mode >>= 6;
else if (in_group_p(0))
mode >>= 3;
if ((mode & mask & (MAY_READ|MAY_WRITE|MAY_EXEC)) == mask)
error = 0;
/* If we can't get a sysctl table entry the permission
* checks on the cached mode will have to be enough.
*/
if (!nd || !depth)
goto out;
dentry = nd->dentry;
table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head);
/* If the entry does not exist deny permission */
error = -EACCES;
if (!table)
goto out;
/* Use the permissions on the sysctl table entry */
error = sysctl_perm(table, mask);
out:
sysctl_head_finish(head);
return error;
}
static int proc_sys_setattr(struct dentry *dentry, struct iattr *attr)
{
struct inode *inode = dentry->d_inode;
int error;
if (attr->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
return -EPERM;
error = inode_change_ok(inode, attr);
if (!error)
error = inode_setattr(inode, attr);
return error;
}
/* I'm lazy and don't distinguish between files and directories,
* until access time.
*/
static const struct file_operations proc_sys_file_operations = {
.read = proc_sys_read,
.write = proc_sys_write,
.readdir = proc_sys_readdir,
};
static const struct inode_operations proc_sys_inode_operations = {
.lookup = proc_sys_lookup,
.permission = proc_sys_permission,
.setattr = proc_sys_setattr,
};
static int proc_sys_revalidate(struct dentry *dentry, struct nameidata *nd)
{
struct ctl_table_header *head;
struct ctl_table *table;
table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head);
proc_sys_refresh_inode(dentry->d_inode, table);
sysctl_head_finish(head);
return !!table;
}
static struct dentry_operations proc_sys_dentry_operations = {
.d_revalidate = proc_sys_revalidate,
};
static struct proc_dir_entry *proc_sys_root;
int proc_sys_init(void)
{
proc_sys_root = proc_mkdir("sys", NULL);
proc_sys_root->proc_iops = &proc_sys_inode_operations;
proc_sys_root->proc_fops = &proc_sys_file_operations;
proc_sys_root->nlink = 0;
return 0;
}
